Thanks @glyn.hudson, I understand a bit more now.
Am I right in thinking the “legacy” format was specifically for the now retired Nodes module? So the emonLCD might be the only thing using the “legacy” format now?
@TrystanLea and I have been discussing MQTT in emonHub and currently agree that there should be 2 main implementations, one that publishes local “status” QoS1 “topic per key” data and the other that publishes a “bulk” type input to deliver data to emoncms in a quick, concise and predictable way that uses QoS 2 to confirm reciept before deleting buffered data.
It seems the emonLCD uses neither of those formats. So we need to look at providing a “node per topic” QoS1 solution too, even if only for backwards compatibility. I think this could be a simple switch setting in the “QoS1 mqtt interfacer”, even if 2 instances are needed to replicate current behavior.
[This is mainly a note to myself to refer back to when I start experimenting with the mqtt stuff in emonhub]